Method for decreasing value of peak power of signals and multi-frequency system for realization thereof

FIELD: electric radio engineering, possible use for increasing quality of electric communication, especially in multi-frequency wireless communication systems.

SUBSTANCE: method for decreasing ratio of peak signal power to its average ratio PAPR in multi-frequency communication systems, in which information symbol is formed by a set of signals, each one of which is centered on one of multiple bearing frequencies, is characterized by the fact that in transmitter a set of bearing frequencies is divided on several sections - subsets of bearing frequencies, information symbol, PAPR value of which does not exceed required threshold PAPR0, is transferred via all carriers, information symbol, value PAPR of which exceeds required threshold PAPR0 is divided on several sub-symbol sections, while number of these sections equals number of sub-carrier subsets, each section of symbol is transferred same as full symbol, wherein data are only transferred on one group of carriers, while other carriers are not modulated, in receiver, arrival of incomplete symbol is identified by analysis of amplitudes of carrier signals, which are not modulated in case of symbol division. Multi-frequency communication system is characterized by construction of receiver and transmitter, adapted for execution of operations, included in proposed method.

EFFECT: preservation of high channel capacity with simplified correction procedure.

2 cl, 12 dwg

 

The invention relates to the field of electrical and radio engineering and can be used to improve the quality of telecommunication, especially in multi-frequency wireless communication. One of the fundamental problems of creating a multi-frequency wireless communication systems and, in particular, systems using OFDM technology (Orthogonal Frequency Division Multiplexing) is the presence of short-term abnormal amplitude of the emission signal, many times exceeding the average value. In order for such a signal was transmitted without distortion, it is necessary to use a digital to analogue Converter (DAC) very large scale (with a large number of quantization levels), which is very difficult from a technical point of view and require large financial expenditures. In addition, increased demands on the value of the linear gain range of the transmitting tract.

Therefore, the problem of reducing the values of the maximum (peak) amplitude of the signal or the instantaneous signal power is extremely important when designing digital transmitter, multi frequency signal.

In the literature the value of the ratio of peak signal power to the average power at the transmission interval is called PAPR (Peak to Average Power Ratio). The PAPR value is measured in decibels. Feature multi-frequency systems and in particular OFDM systems is the fact, is that the resulting signal is a mixture of many signals of subcarriers moreover, the signal on each subcarrier modulated information signal. Thus, for example, OFDM signal consisting of a set of sinusoids with different values of the initial phases and amplitudes (possible number of phases and amplitudes depends on the type of modulation), gives the resulting signal in the time domain may take different values during the transmission interval. Such values may in certain moments of time to significantly exceed the average level. theory of OFDM systems suggests that the distribution of the amplitude of the resulting signal is very close to a normal distribution. In addition to the value of PAPR important parameter is the probability that the maximum power of the signal exceeds this value PAPR. The higher the level of modulation (OFDM systems typically use QAM modulation), the higher the probability of exceeding the peak power of a fixed threshold PAPR.

Known methods and systems for use OFDM technology in wireless communication (see, for example, U.S. patentsâ„–â„–6763591 [1], 6775254 [2], 6771591 [3]). These sources are described, inter alia, the scheme of the transmitter and receiver multi-frequency signal. A block diagram of a typical transmitter multi-frequency signal are presented in Fig 1 Flow of input information symbols distributed over the subcarriers in module 1. Each subcarriers modular which is an information signal in the respective modules 2-7. Streams of modulated subcarriers are combined (multiplexed) into a single output stream in block 8. In OFDM systems, the Association of subcarriers is performed through inverse Fourier transform.

A block diagram of a typical OFDM transmitter is presented in figure 2 binary Input signal passes through the module 9 protective coding (Forward Error Correction Module), then through the block 10 containing interleaver and character encoder (Interleaver+Mapper), and is fed to the input module 11 inverse fast Fourier transform (IFFT). At the output of the module 11, you receive a time signal, which is a mixture of many subcarriers mentioned above. Further conversion modules 12 and 13) associated with digital filtering and then converting the signal in the RF path (modules 14 and 15) and not fundamentally change the situation with PAPR.

Another block diagram of the receiver is presented in the same figure below. The signal passes through the RF path (modules 16 and 17), the ADC 3. Further modules (18-23) perform digital signal processing, Fourier transform, demodulation and decoding, (see for example IEEE P802.11a/D 7.0, July 1999 [4]).

The inverse Fourier transform is recorded by the formula:

where Xk- the complex amplitude of the subcarrier.

Parameter PAPR when this is determined as follows:

the since the samples x can take on different meanings, it is customary to talk about the probability of events when the value of PAPR is greater than some specified value PAPR0:

Pr(PAPR > PAPR0).

In the most similar in design U.S. patent No. 6424681 "Peak to Average Power Ratio Reduction" [5] proposed a method for reducing the PAPR value by reserving part of the subcarriers. Thus one part of subcarriers used for transmission of the information signal, that is, subcarriers modulated information symbols, and the other part of the subcarriers is used to generate a correction signal, which is subtracted from the resulting time signal obtained at the output of IFFT, thereby leading to the reduction of the PAPR0at the same probability value.

Mathematically, this operation is described as follows: part of the subcarriers is modulated by the information signal Xk

zero means that the data carrier is not modulated information symbols (reserved).

When this reserved subcarriers modulated specially selected sequence of characters

such that at the output of IFFT is obtained synthesized signal

where Q is the IFFT matrix formed by the elements

Characters Withkpodbiraut is to minimize the value

The block diagram of the transmitter with redundant subcarriers are presented in figure 3.

The input information signal is distributed over multiple subcarriers in module 1. In this part of subcarriers not used (reserved). After the unification of subcarriers in one time signal in the module 8 is the procedure signal correction module 24 (Kernel Engine) to reduce the PAPR value. This correction is made by adding to the signal x, the correction signal such that the output receive signal with a PAPR value is not greater than the preset threshold. The selection of optimal values of the correction signal is quite complex mathematical relation task, requiring significant time and computing resources. In addition, the disadvantage of this method is the reduction of bandwidth, as part of the subcarriers not used for transmission of information symbols, and to generate a corrective signal.

The task to be solved by the invention, consists in maintaining high bandwidth under the simplified procedure adjustments.

The technical result is achieved by using a new method to reduce the PAPR, which is based on the fact that not every m is egocasting character has time samples of the signal with abnormal deviations of the amplitude. The vast number of characters, in contrast, does not exceed a predetermined threshold PAPR0and thus does not require any additional mitigation measures. And only a relatively small number of characters contains anomalous samples. The data symbols at the transmitter is proposed to be divided into several podskokov, for example two, each of which contains a reduced number of subcarriers modulated input data. The remaining subcarriers are not used, they have zero amplitude. Under the characters will no longer have abnormal deviations of the amplitude, since the reduction of the number of subcarriers the probability of occurrence of anomalous peaks decreases. The receiver also serves to make the detection of such reduced podskokov, to make them demodulation (for this purpose a modified deinterleaver), then merge the demodulated podskokov one so that the output sequence of information symbols coincided with the sequence at full modulation frequency of the symbol; and then further processing (decoding) is similar to the traditional receiver. The block diagram of the receiver for OFDM signal separated by the characters presented in figure 4. The input information data in the module 25 (Smbol Splitter), which distributes the signals on subcarriers. The signals can be distributed on all available subcarriers, and their parts (e.g., half). In the latter case, the DTMF symbol is transmitted several times (in case of double split the first half of the first character, then the second). After this subcarriers modulated in modules 2-7 and are combined in a temporary symbol in module 8.

More partitioning algorithm of symbol 2 posimvol illustrated in Figure 5

The input 32 is sent to the module 25 (Symbol Splitter), which shall decide on the splitting of the full symbol on parsimony. Team decision making is the result of the comparison of the synthesized time pulse with a threshold PAPR0produced in the module 26 (Peak Detector figure 4).

Originally module 25 form a complete character 27 (Full Symbol). After modulation of the subcarriers (module 10) and the conversion time symbol in module 8, make a comparison of peak power time symbol threshold PAPR0. If threshold not, that the full symbol display output. In case of exceeding threshold full character is not output. Instead, the module 25 are split symbol on two posimvol 28 and 29, which are sequentially subjected to the procedure of modulation, the transformation of the project in a temporary character and gives the output. At the same time, because when you generate these characters using only half of subcarriers threshold does not occur. Thus, instead of one full multi-character anomaly threshold is exceeded the output sequentially generates two palusambla without anomalous emission.

Of course, this leads to increased time broadcast information frame, however, since the percentage of abnormal characters to the total number of characters is small, the increase in transmission time is also small. To speed up the generation of multi-frequency symbol should be the procedure of modulation and transformation from the frequency to the time domain for a full character and for its first half in parallel. Then, in case of fixing an anomalous peak in the module 26, the output immediately receive the first half of the symbol. Block diagram of receiver multi-frequency signal with split symbols presented on Fig.6. The input data after the block 21 conversion from the time domain into the frequency received in block 33 of the detection of the arrival of an incomplete symbol (Half/Full Symbol Detector). Since the frequency at which the transmitted information symbols in the case of a split character known (fixed), then the control unit 33 analyzes the amplitude of the signal on subcarriers, which in the case of partitioning the end-of the and positvely not modulated (i.e. their amplitude is equal to zero). Thus comparing, for example, the amount of amplitude (the magnitude of a complex envelope signals on these subcarriers or the sum of the squares of the amplitudes with the corresponding threshold R0you can diagnose the event of the parish incomplete palusambla. In the case of detecting the event of an incomplete symbol demodulator 34 demodulates not all subcarriers, and only those on which the transmitted information symbols. Accordingly deinterleaver 22 converts characters sent on the part of subcarriers in the temporal sequence of characters. When this conversion occurs so that the time sequence remained the same as in the case of transferring full of character. After processing the first palusambla receiver performs the processing of the second palusambla. When this is no longer necessary to detect the event of the arrival of an incomplete symbol, because it is obvious that for the first palacemoon should follow the second. The processing algorithm multi-frequency signal into positvely illustrated by Fig.7.

On Fig shows the block diagram of the transmitter of the OFDM signal is divided into parsimony.

The signal after the protective coding in module 9 enters the module 25, the output of which are formed two sequences of information symbols to complete lots of the frequency of the symbol for half-symbol (first half of the full symbol). Both sequences are parallel conversion in the time domain in blocks 111and 112. The output of block 111(full symbol) analyze module 39 for the presence of abnormal PAPR. If abnormal PAPR is not fixed, the signal available at the output, bypassing standard procedures for adding a guard interval 12, the band-pass filter 13, conversion to an analog signal (14 and 15).

The corresponding block diagram of OFDM receiver with split symbols presented on Fig.9.

The signal after the standard processing modules 16-20 after the FFT block 21 is processed by module 33, which detects the presence of an incomplete symbol, such as symbol, where only half of the subcarriers modulated information signal, and the rest have zero amplitude, i.e. absent. In case of detection of an incomplete symbol demodulation of such incomplete character is using a modified deinterleaver 22, which takes into account the fact that not all subcarriers are used to transmit information. After demodulation of all podskokov, which form the initial full character, and to connect the output information stream so that the order of demodulated symbols correspond to the order of the characters of the original information stream, which is then sent to the decoder 23.

The simulation results presented in Figure 10 and 11. We used the following simulation parameters:

- random characters 107

- modulation 16 QAM

for IFFT 64 points

- tone reservation method:

- the number of reserved tones 10% (6)

- the number of iterations of the gradient method 2 and 4

method of segmenting characters:

the threshold of 8 dB and 9 dB

for IFFT 256 points

- tone reservation method:

- the number of reserved tones 10% (25)

- the number of iterations of the gradient method 2 and 30

method of segmenting characters:

- the threshold of 8.8 dB and 9.5 dB

Calculations for 64-point IFFT show that when the threshold of break characters in 8 dB loss in information rate is 10%, which corresponds to the loss in speed when reserving 10% of the tones. When the powder is e split in 9 dB loss in speed will be 1.9%.

The calculations for the 256-point IFFT show that when the threshold partitioning of characters 8.8 dB loss in information rate is 10%, which corresponds to the loss in speed when reserving 10% of the tones. When the threshold partitioning 9.5 dB loss in speed will be 2.6%. Because the partitioning of the OFDM symbol of the information subcarriers not used, there is a possibility of combining the proposed method with the method of the redundant subcarriers. In this case, the unused subcarriers to generate a correction pulse, which leads to additional reduction of PAPR in cases where any podimore happened excess of signal amplitude (instantaneous power) above the threshold. The block diagram on Fig illustrates a transmitter that uses the split method OFDM symbol together with the generation of the correction pulse unused (reserved) subcarriers.

1. The way to reduce the peak signal power to average power PAPR in multi-frequency communication systems in which information symbol created by the multitude of signals, each of which is centered on one of the multiple carrier frequencies, wherein the transmitter has a set of carrier frequencies is divided into a few parts-subsets of the carrier frequencies, information symbol, the PAPR value of which does not exceed the requirement is been created threshold PAPR 0pass on all bearing, information symbol, the PAPR value of which exceeds the desired threshold PAPR0and is divided into several parts-podskokov, the number of these parts equals the number of subsets of subcarriers, each part of the symbol passed as a full character, in which the data are transmitted only on one part of the bearing, other bearing not modulate, the receiver shall carry out identification of joining incomplete character by analyzing the amplitudes of signals carrying that do not modulate in the case of a split character.

2. The method according to claim 1, characterized in that the bearing is divided into two equal parts, information symbol, the PAPR value of which exceeds the desired threshold PAPR0also divided into two equal parts.

3. The method according to claim 1, characterized in that the bearing part, which when split symbol on positvely not modulate the information signals are used to form the correction signal for reducing the PAPR value of posimvol if it exceeds the required threshold PAPR0.

4. The method according to claim 1, characterized in that after the split of the full symbol on parsimony for each podskokov produce compare the value of the PAPR of posimvol with the required threshold PAPR0if the threshold is not exceeded, podzinger pass, when the threshold is exceeded podengo more the positive break into smaller parsimony, passed on a smaller number of bearing to further reduce the PAPR value.

5. The method according to claim 1, characterized in that the bearing is divided into equal parts; information symbol, the PAPR value of which exceeds the desired threshold PAPR0and is divided into the same number of equal parts.

6. The method according to claim 5, characterized in that after the split of the full symbol on parsimony for each podskokov produce compare the value of the PAPR of posimvol with the required threshold PAPR0if the threshold is not exceeded, podzinger passed on the first part of the bearing, when the threshold is exceeded podengo spread to another part of subcarriers for this part of the subcarriers to produce a comparison value PAPR of posimvol with the required threshold PAPR0if the threshold is not exceeded, podzinger pass on this part of the bearing, when the threshold is exceeded podengo spread to another part of subcarriers redistribution produce up until the requirement for PAPR0will not be executed.

7. Multi-frequency communication system, in which the multi-frequency information symbol created by the multitude of signals, each of which is centered on one of a number of carrier frequencies and which is characterized by the ratio of peak signal power to average power PAPR, consisting of transmitter and receiver, from ecaudata fact, that:

in the transmitter a sequence of information data is received at the input device partitioning, which in accordance with the specified mode of operation is capable of producing output full information symbol or series of podskokov, forming a complete symbol, to another input of the breaker receives the control signal, the output breaker is connected to the input of interleaver, which produces a partitioning of the input data consists of information symbol in the subset, modulating each of the bearing, the output of interleaver connected to the input of the modulator, which modulates the carrier frequency signal signals formed by the subset of data in such a way that its output is a multi-character consisting of a number of carrier, the modulator output is connected to a threshold device which compares the value of the PAPR multi-frequency symbol with the desired threshold, one output of which is connected to the input of the radio frequency path of the transmitter, and the other output is connected with the control input of the split in case if a full DTMF symbol has the value of PAPR is larger than a predefined threshold, a threshold device sends a command to the device partitioning to split lead the character to positvely, each podengo is transmitted at a reduced number of bearing;

in the receiver, in which the input multi-frequency signal fed to the input of the transformation into the frequency domain, performing a selection of General multi-frequency signal, modulating each carrier, the output of the transformation into the frequency domain is connected to the input of the detection of the arrival of an incomplete symbol, which by comparing the amplitude of the carrier is not modulated in the case of splitting a full character on parsimony, with a threshold value to detect the presence of the parish incomplete symbol, the output of the detection device of the parish incomplete symbol is connected to the input of the demodulator, which in the case of a ward full of character demodulates the signal at all frequencies and in the case of receipt of palusambla demodulates the signal part of the bearing, the output of the demodulator is connected to the input deinterleaver, which shall convert the parallel data stream transmitted on multiple carriers in a sequential stream and which in the case of splitting a full character on parsimony converts parallel data stream into a serial stream for each posimvol so that the output serial data stream for a character that has been broken into several podskokov, owls is fully output data stream is full of character.

8. Multi-frequency communication system according to claim 7, in which the multi-frequency information symbol created by the multitude of signals with orthogonal frequency modulation (OFDM, and which is characterized by the ratio of peak signal power to average power PAPR, consisting of transmitter and receiver, characterized in that:

in the transmitter a sequence of information data is received at the input device partitioning, which in accordance with the specified mode of operation is capable of producing output full information symbol or series of podskokov, forming a complete symbol, and the number of podskokov in proportion to the degree 2, to another input of the breaker receives the control signal, the output breaker is connected to the input of interleaver, which produces a partitioning of the input data consists of information symbol in the subset, modulating each of the bearing, the output of interleaver connected to the input of the modulator, which by means of the inverse Fourier transform of the modulating carrier frequency signal signals formed by the subset of information data in such a way that its output is a multi-frequency symbol consisting of a number of carrier, the modulator output is connected to a threshold device in to what the op is comparing the value of the PAPR multi-frequency symbol with the desired threshold, one output of which is connected to the input of the radio frequency path of the transmitter, and the other output is connected with the control input of the split in case if a full DTMF symbol has the value of PAPR is larger than a predefined threshold, a threshold device sends a command to the device partitioning to split the full symbol on parsimony, with each podengo is transmitted at a reduced number of bearing;

in the receiver, in which the input multi-frequency signal fed to the input of the transformation into the frequency domain by a direct Fourier transform, performing the allocation of the total multi-frequency signal, modulating each carrier, the output of the transformation into the frequency domain is connected to the input of the detection of the arrival of an incomplete symbol, which by comparing the amplitude of the carrier is not modulated in the case of splitting a full character on parsimony, with a threshold value to detect the presence of the parish incomplete symbol, the output of the detection device of the parish incomplete symbol is connected to the input of the demodulator, which in the case of a ward full of character demodulates the signal at all frequencies and in the case of the parish palusambla demodulates the signal on the part of the bearing, the output of the demodulator is connected to the input deinterleaver, which implemented yet convert the parallel data stream, transmitted on multiple carriers in a sequential stream and which in the case of splitting a full character on parsimony converts parallel data stream into a serial stream for each posimvol so that the output serial data stream for a character that has been broken into several podskokov coincides with the output data stream is full of character.



 

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SUBSTANCE: system for transmitting discontinuous information contains at transmitting side information sources, multipliers, adder, clock generator, Walsh functions generator, 2n keys (where 2n - number of outputs of Walsh functions generator) and frequency splitter, two elements of one-sided conductivity and 2n additional multipliers, and on receiving side - clock generator, Walsh functions generator, multipliers, integrators, information receivers, 2n keys and frequency splitter, two elements of one-sided conductivity and 2n additional multipliers. As a new addition, on transmitting side two one-sided conductivity elements are inserted and 2n additional multipliers, and on receiving side - two one-sided conductivity elements and 2n additional multipliers.

EFFECT: decreased frequency band due to decreased effective width of channel carriers spectrum.

6 dwg, 1 tbl

FIELD: engineering of communication systems, using multi-access layout based on orthogonal multiplexing circuit with frequency division.

SUBSTANCE: communication system divides whole range of frequencies onto a set of sub-frequency ranges. Receiver of information about quality of channels receives information about quality of channels for each one of a set of frame cells, occupied during first time span by a set of frequency-time cells, occupied by second time span and a given number of sub-frequency ranges, transferred via check communication channel from receiver. Module for sorting frame cells analyzes information about quality of check communication channels and sorts frame cells in accordance to information about quality of channels. Module for assigning sub-channels, if transfer data exist, transfers data through a frame cell with best channel quality among other frame cells.

EFFECT: increased data transfer speed.

5 cl, 6 dwg

FIELD: electric radio engineering, possible use for increasing quality of electric communication, especially in multi-frequency wireless communication systems.

SUBSTANCE: method for decreasing ratio of peak signal power to its average ratio PAPR in multi-frequency communication systems, in which information symbol is formed by a set of signals, each one of which is centered on one of multiple bearing frequencies, is characterized by the fact that in transmitter a set of bearing frequencies is divided on several sections - subsets of bearing frequencies, information symbol, PAPR value of which does not exceed required threshold PAPR0, is transferred via all carriers, information symbol, value PAPR of which exceeds required threshold PAPR0 is divided on several sub-symbol sections, while number of these sections equals number of sub-carrier subsets, each section of symbol is transferred same as full symbol, wherein data are only transferred on one group of carriers, while other carriers are not modulated, in receiver, arrival of incomplete symbol is identified by analysis of amplitudes of carrier signals, which are not modulated in case of symbol division. Multi-frequency communication system is characterized by construction of receiver and transmitter, adapted for execution of operations, included in proposed method.

EFFECT: preservation of high channel capacity with simplified correction procedure.

2 cl, 12 dwg

FIELD: the invention refers to the field of radio technique and may be used for transmission of information with the aid of signals with orthogonal frequency multiplexing.

SUBSTANCE: the technical result is in increasing accuracy of synchronization of signals with orthogonal frequency multiplexing and that in its turn provides reduction of error possibility at reception of these signals even in such complex propagation conditions as shot-wave range channels. For this in the receiving set of the known equipment two memory blocks, two commutators, a maximum choice selection block, a meter and a time intervals calculation block are introduced.

EFFECT: increases accuracy of signals.

6 dwg

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